Electrical thermometer



D ,1930. J. w. ALLEN 1,784,922

ELECTRICAL THERMOMETER Original Filed Aug. 28, 1

1N VENTOR JOSEPH W HALE/v.

Patented Dec. 16, 193.0

UNITED STATES- PATENT OFFICE :osnrn w. ALLEN. or DAYTON. 0310 ELECTRICAL'rnmmonrn'rnn Original application filed August 28, 1924, Serial No.734,817. Divided and this application filed March 16, 1929. Serial No.347,633.

emm mm. mm: ACT or mncn a, 1883, as mmmn APRIL so, 1928; 870 o. e. 757

Q The invention described herein may be manufactured'and used by or forthe Government for governmental purposes without the payililient to meof any royalty thereon.

is invention relates to heat measuring devices generally, and whileparticularly adapted for remote indicating electrical thermometers forindicatin temperature changes in the cooling water 0 airplane enginesand the like, it is capable of adaptation to other forms of devices suchas pyrometers and the like, the present application being a divisional aplication of my former application filed on t e 28th day of August,1924, Serial No.

The principal object of my invention consists in providing relativelycontracting and expanding heat responsive elements for cooperating withan indicating mechanism to indicate the relative change in expansion orcontraction of said heat responsive elements. In carrying out myinvention, I provide two heat responsive elements of a relatively highco-eflicient of expansion which are so connected that when one of saidelements is subjected to heat, it will expand or contract relative tothe other,-causing a movement of an indicator to indicate the amplitudeof the relative movement of said elements.

In the accompanying drawing showing one embodiment of the invention Fig.1 is a front view of the instrument together with a circuit diagram.

Fig. 2 is a diagrammatic view of the mechamcal movement used in theinstrument.

In an airplane installation the instrument 1() will be mounted at someconvenient point in the cockpit and will be connected by conthe case ofan airplane installationwill be ductors 11, 12 and 13, on bindingb'posts11 attery 15,-

immersed in the cooling fluid in order to be affected by the temperaturechanges thereof. The resistance 16 is connected in series with onebranch 17 of a wire loop 18, the latter being grounded and connected asindicated by the connection 19 through the conductor 12 with the battery15. The other branch 20 of the loop 18 is connected as indicated at 21through the conductor 11 with the resistance 14, which in turn isconnected, commonly with the resistance 16, and the battery 15. Withthis brief description it will be apparent that the current flowing inthe branch 17 of the loop 18 is the same asthat flowing throu h theresistance 16. Consequently, upon a c ange in resistance of the variableresistance 16 due to temperature change there will be a change in thecurrent flow through the branch 17 ofthe loop 18. The current flowthrough the branch 20 of the loop 18 remains substantially constantsince it is connected in series with the fixed resistance 14. As will bepresently described, the instrument indicates by elongation of the loop18 the extentof temperature change to which the variable resistance 16issubjected.

The loop 18 is preferably of a very fine-wire having a relatively hightemperatureco-eflicient of expansion, so that small changes in currentflowing therethrough will produce measurable temperature changes, andthereby produce measurable changes in the overall length of the loop 18as the wire expands and contracts.

The two free ends of the loop 18 are rigidly fixed to stems 22adjustable in posts 23 and held b set screws 24. The loop passes over apul e 25 on a. shaft 26 received 1n bearings in t e free end of warm 27,pivoted at 28 to swing in an. arm. A stationarily mounted pulley 29 hasa cord 30 passing over the same connected to a stud 31 on the arm 27 tocommunicate tension to the loop 18, from a coiled spring 32 secured tothe free end of the cord 30 at one end and lodged in a post 33 at theother end. The pulley 25 has a gear 34 arranged to turntherewith uponmovement of the arm 27 when the wireloop 18 elongates or contracts. Thegear 34.

meshes with a pinion 35 to turn a spindle loo 36 to which the needle'37'swinging relative to ascale 38 is rigidly affixed. The scale 38 issuitably calibrated in degrees of temperature change, the needle movingfrom left to right as indicated by the small arrow as the temperature,to which the resistance .16 is subjected, increases. It will be seenthat the loop 18 is constantly under light tension by means of thearrangement shown and that a slight elongation of the branch 17 or aslight contraction thereof, due to a rise or 1 fall of currenttherethrough, will result in a slight movement of the arm 27. In suchmovement the pulley will be caused to rotate, thereby turning the gear34 and causing the gear 35 to swing the needle 37 relative to the scale38.

Aside from the advantage of lightness and simplicity, the instrument isparticularly 1 practical for air lane installations and the like, due tothe act that it may be located 'at a point remote from the place wherethe medium, whose temperature 1s to be taken, is located.

I claim:

1. In an electrical measuring instrument of the character described, awire loop, a pivoted arm for a pulley over which said loop passes,tensionin means normally urging 30 said arm outwar 1y to keep the looptaut, and means carried .by said arm and movable relative to a scaleupon turning of said pulley due to the expansion and contraction of saidloop. a5 2. In an electrical measuring instrument of the characterdescribed, the combination of a loop of flexible wire, a pivoted arm, 'apulley on said arm having sa1d loop passing thereover, a tensioningspring keeping .sai 4 pulley in'position with said loop taut gearing onsaid arm connected to said pulley to i I turn therewith when said armmoves due to the expansion and contraction of said 100 1 a scale, and apointer connected with sa1d gearing movable relative to said scale.

In testimony whereof I aflix my si ature. I JOSEPH W. 'AL EN.

